8 ON SEEDLINGS 



we find a little miniature plant, generally white, sometimes 

 green, but still embedded in endosperm. In otbers, again, tbe 

 endosperm is reduced almost to a film, as in Hippophae (fig. 

 53), and finally, as in the Bean (fig. 51), the embryo occupies 

 the whole seed, and the nourishment intended for the young 

 plant is stored up in the cotyledons themselves. Similarly, in 

 a Walnut, the. two halves of the seed are filled by the two coty- 

 ledons, and attached to them may be found the little plantlet 

 with a delicate white radicle, and a little plumule bearing five 

 or six minute rudiments of leaves, often just tipped with 

 green. 



The Bean and Walnut are instances of exalbuminous or 

 non-endospermic seeds, while those containing endosperm (or 

 perisperm) are termed albuminous. The seed-coat is double 

 in cases where the ovule was provided with two integuments, 

 the outer coat, or testa, developed from the outer integument, 

 being the stronger and often crustaceous in texture. The 

 inner coat or tegmen is thin or soft and delicate, conforming 

 closely to the surface of the endosperm or embryo. It is 

 developed chiefly from the inner integument of the ovule, and 

 is therefore wanting in ovules with only one coat. 



The testa is often provided with appendages or outgrowths 

 of very diverse form and nature, but generally having refer- 

 ence to dissemination of the seed, as in the case of wings or 

 tufts of hair. A more or less incomplete accessory seed-coat 

 is sometimes .formed between the time of fertilisation and 

 ripening of the seed. This is known as an aril Good 

 instances are seen in the Water Lily (Nymphad) and the Yew. 

 Crest-like or wart-shaped appendages developed during the 

 same period are known as strophioles or caruncles. The 

 Castor Oil (Ricinus) supplies a good instance of the latter. 



\ 

 FORMS OF COTYLEDONS. 



I will now pass from seeds to seedlings. No one who has 

 ever looked at young plants can have failed to be struck by 

 the contrast they afford to the older specimens belonging to 

 the same species. This arises partly from differences in the 

 leaves, partly from the contrast which the cotyledons, or seed- 



